D4.1.5 Differences between individuals in adaptation, survival and reproduction Notes

Fitness Drives Natural Selection by Shaping Survival and Reproduction

1. Imagine a pride of lions competing for limited water during a drought.
2. Only those with the strongest adaptations such as endurance or keen senses will survive to reproduce.
3. Over time, these traits become more common in the population.
4. This demonstrates the concept of fitness, and is natural selection in action.

Variation Provides the Raw Material for Natural Selection

1. Populations exhibit variation in traits, which is essential for natural selection to occur.
2. Key Sources of Variation:
   1. Mutation: Introduces new alleles.
   2. Sexual Reproduction: Shuffles alleles into new combinations through meiosis and fertilization.

Intraspecific Competition Creates a Struggle for Resources

1. Individuals within a population compete for limited resources, driving natural selection.
   1. Competition: Intraspecific competition occurs for food, water, mates, and space.
   2. Selection Pressure: Traits that improve access to resources increase an individual’s fitness.

Adaptations to Biotic and Abiotic Pressures Enhance Fitness

• Biotic Adaptations: Traits like camouflage to avoid predators or large antlers to secure mates.
• Abiotic Adaptations: Traits like drought resistance in plants or cold tolerance in animals.

Fitness Shapes the Gene Pool of Future Generations

1. Fitness determines which individuals contribute the most genes to the next generation.
2. These traits can be inherited, meaning individuals with advantageous traits reproduce more, increasing the frequency of those traits in the population.
3. Or, populations can evolve as traits that improve fitness become more common.

Reflection

1. Natural selection is a powerful process that explains how populations adapt and evolve over time.
2. By understanding the roles of variation, fitness, and competition, we gain insight into the mechanisms that drive biodiversity on Earth.